1. Field of the Invention
The invention relates in general to a calibration technology, and more particularly to a calibration technology for a display device.
2. Description of the Related Art
Ensuring normal functionality of products when the products are shipped out of the factory is always a focus of manufacturers. By pre-filtering out and repairing problematic products, post-sales returns and exchanges can be effectively prevented to increase customer satisfaction.
For a display device, a common test item is inputting data of a reference image at a signal receiving end of the display device, and an actual display result is monitored to ensure its correctness. For example, referring to FIG. 1, the reference image may include multiple vertical gray lines having different brightness levels (gradually increasing from left to right). Assuming that a grayscale range that the display device provides is 0 to 255, the reference image may include gray lines having a maximum of 256 different brightness levels. Known to one person skilled in the art, grayscale values of the three primary colors—red, green and blue, in gray pixels, are equal. When a reference image is displayed by a screen under test, as a reflection on unsatisfactory color linearity of the screen under test, an image presented by the screen under test may include non-gray pixels. Once the above problem is identified, settings (e.g., a gamma curve) are usually manually adjusted by testing personnel to correct lines with abnormal colors to expected gray lines.
In the prior art, testing personnel mostly determine rough positions of the abnormal lines by the naked eye, and gradually approximate actual positions of the abnormal lines starting from the rough positions. Having locked precise positions of the abnormal lines, the testing personnel then start adjusting image characteristic parameters of the abnormal lines. Assume that an abnormal line appears at a position 20A in FIG. 2. The position 20A falls in a central region and slightly to the right in the overall reference image, and thus the testing personnel may preliminarily determine that the grayscale that needs to be adjusted in the gamma curve is close to but slightly higher than the grayscale value 128. In one approach for identifying the exactly grayscale value corresponding to the position 20A, a signal source is controlled to intentionally set a vertical line corresponding to the grayscale value 128 in the reference frame to a distinct color that can be easily identified (e.g., pure red in a high brightness level), and to further mark a position of the line corresponding the grayscale value 128. Next, the testing personnel may gradually change the position of the reference line having the intentionally changed color, e.g., sequentially changing the color of the vertical lines corresponding to grayscale values 129, 130, 131 . . . , until the reference line overlaps with the abnormal line. With the confirmed grayscale value corresponding to the abnormal line, the testing personnel can then adjust the image characteristic parameters corresponding to the grayscale value in the gamma curve.
The above calibration solution may be extremely time-consuming. For multiple abnormalities occurring in a same screen under test, the calibration procedure for the screen under test may take up an entire day, and is thus quite uneconomical.